The present invention relates to alignment tools, and in particular, to an alignment tool and a method of making and using the alignment tool to align an antenna such as the antenna of a base station of a wireless communications system.
Wireless communication systems are constructed by placing wireless device, such as antennas, in strategic locations and aiming the antennas so that information can be transmitted and received between antennas in neighboring cells and to areas within the antenna""s cell. Typically the antennas are mounted on the top of a tower using a triangular structure or hat 200 depicted in FIG. 7. The triangular structure 200 includes three antenna arrangements 210, 220, and 230 that are aimed along azimuths 218, 228, and 238, respectively, that are each separated by 120 degrees and are designed to transmit and receive information within a sector in front of the respective antenna arrangements. The antenna arrangements 210, 220, and 230 each include three individual panel antennas or sectored antennas that transmit energy in a specific direction. Specifically, antenna arrangement 210 includes antennas 212, 214, and 216, antenna arrangement 220 includes antennas 222, 224, and 226, and antenna arrangement 230 includes antennas 232, 234, and 236. The antennas are conventionally mounted to the triangular structure 200 by attachment to a standard 2xc2xd inch pipe 202.
In order to provide full and continuous coverage within each cell of a wireless communication system, proper alignment of each individual antenna is essential. A great deal of resources are spent in developing and optimizing wireless networks to accommodate as many users as the system will bear. Since a wireless communication system operates in a celled layout, each individual antenna is responsible for not only transmitting information to and receiving information from customers within their respective cell, but also for relaying information from cell site to cell site. If a single antenna in the wireless communication system is improperly aligned, an area within the wireless communication system is created that is not properly covered by an antenna. The result of having an improperly aligned antenna is the creation of an area in which the customer will receive poor transmission and reception quality or will receive no signal, thereby leaving a hole in the wireless communication system. A second result of having an improperly aligned antenna is an overall system performance problem due to the resulting poor relay signal. Realignment of an incorrectly aligned antenna is extremely costly as it requires a substantial amount of time to travel to the cell site, align the antenna and test the cell in order to ensure the problem has been corrected.
Currently antennas are aligned using a magnetic compass. An engineer typically determines the direction of the proper azimuth, and a technician aligns the antennas according to the reading of the compass essentially so that the antenna beam points along the compass heading matching the designated azimuth. The use of a compass to align the antennas can be very inaccurate since the antennas are typically mounted at the top of a steel tower or structure that can cause significant interference (e.g., xc2x120 degrees) with the magnetic reading of the compass. The accuracy of the alignment may not be immediately detected by the engineer, but rather may be detected by complaints from customers or through sampling of the signal from the antenna throughout the coverage area of the antenna.
Consequently, a need exists for a tool that can be used to accurately and efficiently align an antenna, thereby reducing the need for realignment of the antenna. Additionally, the accuracy of the alignment tool should not be susceptible to interference from the surrounding structure upon which the antenna is mounted.
The present invention provides an alignment tool and a method of making and using the alignment tool to accurately and efficiently align an antenna along an azimuth. The present invention achieves this result by providing a tool having indicium thereon to allow an engineer to align the tool with the antenna and to align the tool with a predetermined landmark. The alignment tool of the present invention overcomes the disadvantages of using a magnetic compass since the tool does not use magnetism to align the antenna and, therefore, is not susceptible to interference from the surrounding structure upon which the antenna is mounted.
The present invention advantageously provides an embodiment that includes a transparent substrate that is preferably planar and is made of a lightweight, durable, shatterproof sheet of material such a clear plastic. The tool includes a series of indicia that enable the tool to be used to align an antenna with its respective azimuth. The alignment tool includes a receiving portion adapted to receive a mounting structure of the antenna The receiving portion of the tool includes an axis and is configured such that when the tool receives the mounting structure an adjustment axis of the antenna is coaxial with the axis of the tool.
The tool preferably includes a bearing indicium, a reference indicium, and at least one landmark indicium. The bearing indicium is used during the making of the tool and represents an azimuth along which the antenna is to be aligned. The reference indicium is used during the alignment of the antenna to align the tool with the antenna. Generally, speaking the reference indicium is shaped to match a known feature on the antenna, for example a rear surface thereof, and to provide a reference such that when the reference indicium is aligned with the known feature on the antenna then the bearing indicium should be aligned with the transmission direction of the antenna. The landmark indicium is used during the alignment of the antenna to align the tool with a distant landmark. The bearing indicium and the landmark indicium are positioned along a radial extending from the axis of the tool. The landmark indicium is oriented on the transparent substrate such that when the landmark indicium is aligned along a radial extending from the axis of the tool to the landmark, the bearing indicium is aligned with the azimuth and the reference indicium can then be used to align the antenna with the azimuth.
The alignment tool is constructed using a topographical map that includes geographic markings for the antenna, the azimuth corresponding to the transmission direction of the antenna, and a distant landmark. Once the topographical map is constructed and the layout on the topographical map is complete, the transparent substrate having an axis and a bearing indicium marked thereon is positioned on the map such that the axis is directly aligned with the marking for the antenna and the bearing indicium is directly aligned with the marking for the azimuth. The landmark indicium is then made on the transparent substrate along a radial extending from the marking for the antenna to the marking for the landmark.
Once the landmark indicium is formed on the tool along with the reference indicium and the bearing indicium, the alignment tool is brought to the top of the tower for alignment of the antenna. The receiving portion of the tool is slid over the mounting structure of the antenna such that the tool is positioned above the antenna. The preferred method of using the tool includes an engineer obtaining a vantagepoint above the antenna and aligning the reference indicium such that it is parallel to an edge on a rear surface of the antenna. The transparent nature of the substrate will allow the engineer to view the edge through the substrate. The method of using the alignment tool further includes pivoting the antenna about the adjustment axis and pivoting the tool about the axis of the tool until the landmark indicium is directly aligned with a radial extend from the axis of the tool to the landmark. The antenna should now be aligned with the correct azimuth.
Additional advantages and other features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the invention. The advantages of the invention may be realized and obtained as particularly pointed out in the appended claims.